The invention relates to an areally extended composite material with fibers and plastic impregnation, and to methods for the manufacture of and to uses of composite materials of this kind.
A method, namely a pressure impregnation, is known from DE-A-41 21 915 in which an endless reinforcement fiber cord is impregnated with a thermoplastic polymer. In this method the fiber cord is first impregnated with firm thermoplastic particles in a bath which contains a dispersion of the particles. After the impregnation bath the dispersion medium is evaporated out of the impregnated fiber cord in a drying oven. Then the dry fiber cord is passed through an oven in which the particles melt. After a consolidation a small band-like fiber composite material with a firm polymer matrix is present. Small bands of this kind can be arranged to form webs, meshes or grids and formed to areally extended composite materials through a pultrusion in which the polymer matrix is temporarily melted again. Composite materials of this kind can also be brought into the shape of a profiled bar.
Areally extended composite materials are suitable for reinforcing components which are used in building construction, vehicle construction, light construction or the construction of apparatuses and devices. For reinforcement the composite material is applied to the component with a connecting medium, i.e. with an adhesive.
In reinforcements of components, flexible webs of fiber cords are also used which are adhesively bonded with a plastic mass onto partial surfaces of the component to be reinforced. Reinforcements of this kind are carried out primarily at curved surfaces and at edges. In practice however problems occur in this reinforcing method. The fiber cords of the flexible web can be displaced with respect to one another so that an irregular structure easily arises which is deformed by humps. A web which is deformed in this manner can no longer be applied flatly onto the surface to be reinforced. For a maximum stiffness and strength of the reinforcement, the fibers would have to be completely aligned; a fiber alignment of this kind is however not possible with a deformed web.
It is an object of the invention to create an areally extended composite material and methods for manufacturing composite materials of this kind which are suitable for the reinforcement of curved surfaces and edges.
The areally extended composite material contains fibers which are impregnated with plastic. The composite material comprises at least two arrays of parallel fiber cords which extend in different directions and which form a web, mesh or grid. The fiber cords can be bundle-like or band-like. The fibers of a first array are impregnated with substantially more plastic than the fibers of a second and possibly of a further array. The composite material is stiff in the direction of the fibers of the first array and is flexible transversely to this direction. Openings advantageously exist between the fiber cords.
Using the composite material in accordance with the invention, which is semi-flexible, components in the above-named fields can be reinforced at edges or cylindrical partial surfaces. In this it can be adhesively bonded or welded on in one or more layers. During the adhesive bonding it is advantageous when openings exist between the fiber cords. Thanks to the partial stiffening and a mutual fixing of the fiber cords, which are arranged transversely to one another, the danger of unfavorable deformations of the composite material in accordance with the invention is excluded.
The invention will be explained in the following with reference to the drawings.